Response analysis of fluorescence parameters of tomato seedlings oriented to vertical light environment adaptation

Seedling quality greatly affects the subsequent survival, quality and yield of tomatoes. To explore the response of tomato seedlings on vertical light, we investigated the continuous trends of chlorophyll fluorescence parameters in six vertical light intensities and Pearson's correlation analysis of them. The results showed that the dark fluorescence parameters of F_m, F_v/F_m highly correlated with the photosynthetic photon flux density (PPFD) while NPQ, Y(NPQ), Y(NO) were highly correlated with the day of light processing (DLP). With increasing PPFD, the F_v/F_m decreased, the residual sum of curves increased and the scaling factor (S) was decreased. The photoinhibition phenomenon was relieved to different degrees on DLP 4. L4 (243.17 ± 4.37 μmol m^-2 s^-1) was the fastest light adaptation, L5 (295.34 ± 5.42 μmol m^-2 s^-1) was the second. Φ_PSII accumulation was greatest in L4 and second in L5. Both L4 and L5 seedling health index and dry weight were significantly higher than L1 (53.20 ± 1.55 μmol m^-2 s^-1). L4 had the highest Chl a/b and total soluble sugar. It can be concluded that L4 was the best vertical PPFD with the highest light-adaption. The larger the PPFD, the greater the curve deviation, the greater the degree of data discretization, and the higher the photoinhibition. The more appropriate the light intensity is, the faster the seedlings light-adapted are. Therefore, the rapid and proper adjustment of light intensity is the key to obtain high quality tomato seedlings.